In a secondary battery device comprising an assembled battery including a plurality of secondary battery cells, the voltage of each of the secondary battery cells, the temperature of the assembled battery, and the like are constantly monitored, in order to avoid the secondary battery cells from being overdischarged or being in an abnormal state.
Further, in general, in an assembled battery that uses a plurality of secondary battery cells combined in series, the energy stored in the combined secondary battery cells becomes uneven, due to overdischarge or unevenness in temperature of the secondary battery cells.
The unevenness in energy stored in the secondary battery cells makes it impossible to perform efficient overdischarge that can maximize the function as an assembled battery. Conventionally, a resistive discharge method has been proposed as a circuit for equalizing the energy.
In a conventional voltage correction circuit of a secondary battery, unevenness in voltage or capacity of the battery is judged, and a battery with a high energy is connected to a resistance and let the battery discharged. Further, the battery voltage correction device of a conventional assembled battery performs a discharge process so as to adjust the level before charge. Further, according to a conventional battery group control device and a battery power system, an approach of measuring the energy between the unit cells at a no-load voltage, calculating the remaining capacity between the unit cells, and bypassing the charge/discharge current of a cell having a deviation equal to or greater than a set value with respect to an average remaining capacity of the unit cells.
A secondary battery device that equalizes the energy comprises an assembled battery module provided with an assembled battery including a plurality of secondary battery cells and an assembled battery monitoring circuit, and a control device (MPU) configured to control the operation and the like of the assembled battery monitoring circuit, for example. The assembled battery monitoring circuit is provided with an equalization processing module configured to discharge the secondary battery cells. The control device is fed from an external power source provided outside.
In order to prevent deterioration of a battery by preventing an adverse effect caused by the equalization circuit on the battery when a battery for an electrical component that is used as an external power source is broken, or when a power source line of a battery for an electrical component is broken, e.g., disconnected, a power source device for a vehicle including a stop circuit for stopping an equalization circuit has conventionally been proposed.
A relatively long time is required to discharge a secondary battery cell in which a high energy is stored and to equalize the energy of a plurality of secondary battery cells forming an assembled battery. Further, when a lithium ion battery is adopted as a secondary battery cell, in particular, the voltage or temperature of the secondary battery cells needs to be constantly monitored so as to avoid heat generation, for example, due to overdischarge.
On the other hand, when a control device for controlling an assembled battery monitoring circuit is constantly monitored, it is difficult to suppress consumption of the external power source. In particular, when insulating communications are performed in an interface circuit between an assembled battery monitoring circuit and a control device, it was difficult to suppress power consumption in an insulating communication circuit. Accordingly, forming a secondary battery device such that the voltage detecting module or the equalization processing module of the assembled battery monitoring circuit can perform energy equalization, even during the period while the feed to the control device is stopped, has been contemplated.
In that case, however, even if the assembled battery module is removed from a control device for replacement, for example, since the energy stored in the assembled battery is consumed when the assembled battery monitoring circuit continues monitoring voltages of the secondary battery cells or equalizing the energy, it has been difficult to achieve low power consumption.